Psychiatric morbidity has been associated with HIV disease since the beginning of the AIDS epidemic. Most of the clinical literature to date has focused on psychiatric issues in men who are HIV seropositive. There has been little data regarding the prevalence of psychiatric disorders in HIV infected women, despite the fact that HIV remains among the leading causes of death for US women between the ages of 25 and 44. HIV also is the leading cause of death among African American women in this age group. We found that the proportion of women with current major depression was four times higher in HIV positive women compared to HIV seronegative women. This high rate of major depression coupled with the recent and largest epidemiology study to date indicating that depression is associated with increased mortality in HIV-infected women, underscores the need for studies to ascertain the relationship of major depression, immunity, and HIV disease progression in HIV infected women. The potential immune mechanisms by which depression may influence HIV disease progression and mortality remain to be understood. In our studies of HIV infected men, we have found depression associated alterations of immune cytotoxic cells suggesting that killer lymphocytes might mediate the effects of depression on HIV disease progression. Although previous studies have focused almost exclusively on HIV infected men, we have recently found that women with depression exhibit significant reductions in natural killer cell activity as well as increases in activated CD8 lymphocytes and viral load. The proposed study of HIV seropositive women, largely of minority representation, is designed to provide important information on 1) the underlying immune mechanisms by which depression my influence HIV-1 replication and thereby HIV disease progression; and 2) three potential mechanisms of action whereby depression my influence immunity and HIV disease progression. The present study may also help determine whether conventional antidepressants (SSRIs) as well as novel antidepressant pharmacotherapies (substance P antagonists and glucocorticoid antagonists) might benefit HIV-infected individuals and extend survival with HIV infection.